Time (Mis-)Alignment when Recording

[philbrown]

Is it always such a bad thing that signals don't arrive at the same time? Microphones never line up. Two people singing into the same mic, unless they stand still and measure their marks, will never arrive at the same time. It's part of what gives sound its character, and certainly the reflections in an acoustic space will cause immense variability of signal return, so why not electronic gear? Unless you're doing scientific research that requires it. Or if it's the equivalent of having a singer perched in a tree on the back lot.

Yes, but your example is based around different sound sources. On the same source, such as mic'ing a guitar amp it's a big deal to get the mic capsules lined up exactly or it's phase city. My guitar tracks absolutley sound better and fuller when they are time aligned, and have various amounts of out-of-phase-ness when they don't. Your example is more like double-tracking guitars which is a whole different animal and you couldn't time-align those (in the way we are discussing) even if you wanted to.

[philbrown]

One more thought - I just tracked and mixed a bunch of drum tracks and I tried something I read about where you delay the snare and kick mics to line up with the overheads. There are various ways and plugs to do this and I tried several, some of which you can enter inches or centimeters by actually measuring the distances with a tape measure. I ended up liking the mics straight up and took all that stuff off by the end of the project and was very happy with the drum sound. It's hard to describe exactly what the difference sounded and felt like, but it just sounded better without that stuff. Probably just what our ears have become accustomed to over the years.

[mikehalloran]

Summing to mono is an easy check for phase anomalies. If you find them, then you decide, will this track ever be heard in mono?

I used to record large choirs using ORTF micing. The bottom end dropped right out when summed so I switched to M+S which sums quite well. I never tried to fix the ORTF recordings, though — I figured that mono didn't really matter with these.

[HCMarkus]

One more thought - I just tracked and mixed a bunch of drum tracks and I tried something I read about where you delay the snare and kick mics to line up with the overheads. There are various ways and plugs to do this and I tried several, some of which you can enter inches or centimeters by actually measuring the distances with a tape measure. I ended up liking the mics straight up and took all that stuff off by the end of the project and was very happy with the drum sound. It's hard to describe exactly what the difference sounded and felt like, but it just sounded better without that stuff. Probably just what our ears have become accustomed to over the years.

When recording a drum kit, I usually have a mono room mic picking up the kit from a distance. Varying level, EQ and compression and shifting the time of the distant mic give a huge palette of spacial and tonal textures. I don't use plug-ins to shift drum track timing; I just do it by eye and ear in DP.

[philbrown]

When recording a drum kit, I usually have a mono room mic picking up the kit from a distance. Varying level, EQ and compression and shifting the time of the distant mic give a huge palette of spacial and tonal textures. I don't use plug-ins to shift drum track timing; I just do it by eye and ear in DP.

I should have done that on this last project. Note to self and thanks for the reminder HC.

[magicd]

One more thought - I just tracked and mixed a bunch of drum tracks and I tried something I read about where you delay the snare and kick mics to line up with the overheads. There are various ways and plugs to do this and I tried several, some of which you can enter inches or centimeters by actually measuring the distances with a tape measure. I ended up liking the mics straight up and took all that stuff off by the end of the project and was very happy with the drum sound. It's hard to describe exactly what the difference sounded and felt like, but it just sounded better without that stuff. Probably just what our ears have become accustomed to over the years.

Let's say you have a traditional drum mic setup with close mics and overheads. Let's say one overhead is five feet from the snare mic. If you are using multiple overheads you may want those mics to be equal distance from the snare. Of course if you do that they won't be equal distances from the toms for example, but that's a different consideration.

If the overhead is five feet from the snare it is roughly 5 ms behind the direct snare in the recorded track.

I've seen engineers move the overhead audio tracks so the OH snare hits line up up with the direct track. Now the cymbals are 5 ms early but maybe that's not a phase problem if the direct mics are gated.

If you leave the overheads in their original position you might like the ambience you get from the directs and overheads. Personally when I mix drums I start with the overheads and then bring in the direct mics for clarity and punch.

So speaking strictly for myself I like the delay between the overheads and direct mics. That's individual taste.

But delay offset and phase relation are not exactly the same thing. For example let's say you play a sine wave from a speaker and you have two mics on the speaker, one further away from the other. Both mics pick up a sine wave that may or may not be phase accurate in their time-relation. You could then make very small adjustments to the distance of one of the mics to change the phase relationship. That will make a big difference to the combined sound of the two mics, regardless of the initial ambient delay.

I use the Precision Delay plug-in when I'm messing with phase related signals. Simple test: Record a guitar amp with two mics, one close and one far. Put the Precision Delay on one of the mics. To really hear the phase relation of the two signals make them mono. Change the delay forwards or backwards of one of the mics and you will hear a dramatic difference in tone.

You can do the same thing with drum overheads. You can keep the 5 ms or so offset between the overheads and direct mics, but you can also make very small changes forwards or backwards that will influence the phase relationships of the signals.

Hope that helps!

Dave

[philbrown]

Excellent info as always MagicD!
I do measure my O/H mics and have them equidistant to the snare and *roughly equidistant to the kick as much as possible. Hadn't considered the phase relationships though as it applies here. Always something new to learn in recording.